Tripod type constant velocity joints are well known in the automobile industry as one type of constant velocity joints used in the drive system of vehicles for transferring a uniform torque and a constant speed, while operating with a wide range of joint angle.
For instance, one example of the tripod type constant velocity joint was illustrated in Japanese Patent Application, S62-233522. This tripod type constant velocity joint typically includes tripod fixed to an end of the second rotating shaft, which functions as a driven member, and hollow cylindrical housing fixed to an end of the first rotating shaft which functions as a drive member. Three circumferential grooves are formed at three locations on the inner face of the housing at equal spacing in the circumferential direction and extend in the shaft direction of the housing. Each tripod comprises a boss connected to the second rotating shaft, and each trunnion has a cylindrical shape and extends radially from three locations at equal spacing around the boss. Each trunnion has a roller fixed at a distal end of the trunnion and with needle rollers engaged therein. In this arrangement, each roller can freely rotate about the trunnion while also be displaced in the axial direction of the trunnion. The constant velocity movement between the first and second rotating shafts is ensured with the rollers rotatably and displaceably engaging in the grooves disposed along the inner face of the housing. In order to facilitate the sliding movement, a pair of side faces are formed in circular recesses on each side of the respective grooves, and each roller is supported rotatably and pivotally along the side faces of the grooves.
When the first and second rotating shafts rotate with a joint angle present between the first and second shafts, each roller moves with complexity. For example, each roller moves in the axial direction of the housing along each of the side faces of the respective guide grooves, while the rollers change in orientation and further displace in the axial direction of the trunnion. Such movement of the rollers cannot cause a relative movement between a peripheral outside face of each of the rollers and each of the side faces to be smoothly made. Thus, a relatively large friction occurs between the faces. As a result, this tripod type constant velocity joint produces three-directional axial forces as the shafts rotate. In the application of a prior art tripod joint to the vehicles, it is known that the axial forces may cause a transverse vibration typically referred to as “shudder”. This shudder disturbance may become severe particularly when a large torque is transmitted with a relatively large joint angle present.
Moreover, various suggestions and attempts were made to improve the functions or operability of the constant velocity joint. For example, FIG. 1 illustrates one known structure of a tripod type constant velocity joint, in which a spider (or trunnion) 11 is operably received in housing 12 with a roller assembly assembled to the spider 11 for transmitting torque between first and second rotating shafts. The roller assembly received in a guide groove of the housing 12 is composed essentially of outer roller 13′, inner roller 14′, and multiple needle rollers 15 engaged between the outer and inner rollers 13′ and 14′. In this example, the inner roller 14′ has a cylindrical surface on the outer diameter thereof, and the outer roller 13′ has a cylindrical surface on its corresponding inner diameter thereof, in which the cylindrical surfaces do not include any taper angle present to accommodate needle rollers 15 between the opposing cylindrical surfaces of the inner and outer rollers 14′ and 13′. In this structure, clearance δ1 is present between the outer surface of the inner roller 14′ and the needle rollers 15 (or between the inner surface of the outer roller 13′ and the needle rollers 15), which is constant throughout the length due to the opposing and parallel cylindrical surface configurations of the roller assembly regardless of the axial movement or position of the inner roller 14′ in the roller assembly. As shown in FIG. 1, the outer roller 13′ includes an inwardly-projecting portion “AA” in order to prevent the outer roller 13′ (or the inner roller 14′) from separating from the inner roller 14′ (or the outer roller 13′) of the roller assembly.